lkml.org 
[lkml]   [2009]   [May]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/3] tracing/stat: sort in ascending order
On Mon, May 25, 2009 at 04:46:09PM +0800, Li Zefan wrote:
> Currently the output of trace_stat/workqueues is totally reversed:
>
> # cat /debug/tracing/trace_stat/workqueues
> ...
> 1 17 17 210 37 `-blk_unplug_work+0x0/0x57
> 1 3779 3779 181 11 |-cfq_kick_queue+0x0/0x2f
> 1 3796 3796 kblockd/1:120
> ...
>
> The correct output should be:
>
> 1 3796 3796 kblockd/1:120
> 1 3779 3779 181 11 |-cfq_kick_queue+0x0/0x2f
> 1 17 17 210 37 `-blk_unplug_work+0x0/0x57
>
> It's caused by "tracing/stat: replace linked list by an rbtree for sorting"
> (53059c9b67a62a3dc8c80204d3da42b9267ea5a0).
>
> Though we can simply change dummy_cmp() to return -1 instead of 1, IMO
> it's better to always do ascending sorting in trace_stat.c, and leave each
> stat tracer to decide whether to sort in descending or ascending order.
>
> [ Impact: fix the output of trace_stat/workqueue ]
>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>


For now in stat tracing, the ascendent sorting is the most relevant.
Especially because we always want to see the highest problems first.

-1 (or < 0) usually means lower and 1 ( > 0) is higher.
I wonder what would most confuse the developers of stat tracers:

- to reverse these common sort values (-1 turn into "higher")
- keep the default ascendent sorting, which is not natural because the default
is often descendent.

I don't know.

Anyone else. Do you have a preference?

Thanks,

Frederic.


> ---
> kernel/trace/ftrace.c | 12 ++++++------
> kernel/trace/trace_branch.c | 5 +++--
> kernel/trace/trace_stat.c | 6 +-----
> 3 files changed, 10 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 140699a..3dd16bd 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -315,29 +315,29 @@ static void *function_stat_start(struct tracer_stat *trace)
> }
>
> #ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -/* function graph compares on total time */
> +/* function graph compares on total time in reverse order */
> static int function_stat_cmp(void *p1, void *p2)
> {
> struct ftrace_profile *a = p1;
> struct ftrace_profile *b = p2;
>
> - if (a->time < b->time)
> - return -1;
> if (a->time > b->time)
> + return -1;
> + if (a->time < b->time)
> return 1;
> else
> return 0;
> }
> #else
> -/* not function graph compares against hits */
> +/* not function graph compares against hits in reverse order */
> static int function_stat_cmp(void *p1, void *p2)
> {
> struct ftrace_profile *a = p1;
> struct ftrace_profile *b = p2;
>
> - if (a->counter < b->counter)
> - return -1;
> if (a->counter > b->counter)
> + return -1;
> + if (a->counter < b->counter)
> return 1;
> else
> return 0;
> diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
> index 7a7a9fd..df58411 100644
> --- a/kernel/trace/trace_branch.c
> +++ b/kernel/trace/trace_branch.c
> @@ -301,9 +301,10 @@ static int annotated_branch_stat_cmp(void *p1, void *p2)
> percent_a = get_incorrect_percent(a);
> percent_b = get_incorrect_percent(b);
>
> - if (percent_a < percent_b)
> - return -1;
> + /* sort in descending order */
> if (percent_a > percent_b)
> + return -1;
> + if (percent_a < percent_b)
> return 1;
> else
> return 0;
> diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
> index 2e849b5..6efbcb4 100644
> --- a/kernel/trace/trace_stat.c
> +++ b/kernel/trace/trace_stat.c
> @@ -98,10 +98,6 @@ insert_stat(struct rb_root *root, struct stat_node *data, cmp_stat_t cmp)
> {
> struct rb_node **new = &(root->rb_node), *parent = NULL;
>
> - /*
> - * Figure out where to put new node
> - * This is a descendent sorting
> - */
> while (*new) {
> struct stat_node *this;
> int result;
> @@ -110,7 +106,7 @@ insert_stat(struct rb_root *root, struct stat_node *data, cmp_stat_t cmp)
> result = cmp(data->stat, this->stat);
>
> parent = *new;
> - if (result >= 0)
> + if (result < 0)
> new = &((*new)->rb_left);
> else
> new = &((*new)->rb_right);
> --
> 1.5.4.rc3
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/



\
 
 \ /
  Last update: 2009-05-25 17:45    [from the cache]
©2003-2011 Jasper Spaans